Many types of prosthetic devices are available for amputees. These devices may be constructed for attachment to a mounting system arranged to secure the device to the wearer. Conventional mounting systems may include an open-ended socket for receiving and supporting an amputee's residual limb. In lower leg prostheses, straps and other fasteners are often provided for securing the prosthesis to the residual limb to accommodate walking mobility at least limitedly. The ability to achieve full use of a prosthetic limb is an important factor in both the physical and mental rehabilitation of an amputee.
Properly fitting and securing a prosthetic device to an amputee is often difficult because residual limbs can be various shapes and sizes and their volume may fluctuate. Older residual limbs may have experienced atrophy and are generally more conical in shape, while many newer residual limbs are slightly bulbous or cylindrical in shape. Residual limbs may be characterized by various individual characteristics, including the volume and shape of the limb, scars, skin grafts, bony prominences, edema or soft tissue configurations. Conventional prosthetic device mounting systems do not fit snugly on an amputee and are typically not comfortable to wear.
A proper fit of the prosthetic device on a residual limb is essential to ensure adequate mobility and safety. In walking, compressive loading of the soft residual limb tissue can cause blisters, sores, chafing, and other undesirable skin irritation problems. Conventional mounting systems that attempt to correct these deficiencies by including additional soft padding within the socket are disadvantageous since the extra material can interfere with forming an optimal connection.
One way in which a prosthetic device can be attached to a residual limb is by using suction or vacuum pressure. Such an arrangement often includes using liners worn on the residual limb. These liners can be made from a soft, stretchy material that acts as an interface with the prosthesis. Once the liner is on, the residual limb can then slide into a hard socket made to fit the shape of the residual limb.
When attaching a prosthetic device to a wearer, the socket must be securely fitted to the limb to hold it in place during movement. Maintaining stability for the wearer is a common problem, since many existing anchoring systems use a single attachment point to hold the residual limb in place. This type of arrangement may lead to extraneous pivoting, rotating, and shifting of the residual limb, especially during ambulation for lower body limbs, such as lower leg and knee prosthetics.
It is important to be able to periodically adjust the anchoring system since the mass of the limb may change throughout the day. Residual limbs can change size due to swelling or contracting depending on factors such as how they are used, their frequency of use, and the temperature. Minor protuberances inside the socket can be uncomfortable and cause unbearable pain to an amputee.
Some conventional anchoring systems with generally cylindrical sockets may be secured to a residual limb via a radial pressure fit. This type of system is not ideal since radial pressure imposed on a limb received in a hard socket squeezes it unevenly and adds to the discomfort felt by the amputee. The fit obtained may not be secure since radial pressure can cause the limb to pop out of the socket over a day making the system unreliable for a wearer.
Alternatively, Velcro or Chicago screws have traditionally been used to attach an insert to a socket retainer. This arrangement is functional when using a standard expulsion or vacuum system sealed proximally with a sealing sleeve. Modern sockets with flexible liners may have cutouts over boney prominences or utilize internal socket seals. These newer sockets cannot accommodate a flexible insert in combination with a vacuum or expulsion valve because the vacuum or expulsion system is housed in the outer retainer. This is undesirable because air would enter the system proximally between the inner flexible insert and the rigid retainer. For a vacuum or expulsion system to work, the vacuum or expulsion system in the distal portion of the retainer would have to be connected to the flexible inner insert distally as in the present disclosure.
When a lower limb amputee ambulates using a conventional prosthesis, air inside the socket may cause the prosthesis to slip from the amputee during the swing phase of a normal gait cycle. This causes an accelerated impact of the residual limb at the bottom of the socket when the heel hits the floor. By removing air from the cavity, the prosthesis can be held closer to the residual limb during the swing phase, thus reducing the accelerated impact at heel strike. There are many ways to remove the air, including an expulsion valve. Conventional expulsion valves, however, are installed in or through the walls of the socket, which is not optimal.
There are many types of one-way valves, including spring valves. Spring valves use a spring to urge a stopper to resist air from traveling in one direction while allowing the air to travel in the other direction. The disadvantage of using spring valves is that air must accumulate enough force to overpower the spring and open the valve. The consequence of this is that the spring will close the valve before most air escapes the socket, which is called “cracking pressure.” It is not desirable to allow air to come back through the valve as weight is relieved from the prosthesis during the swing phase of ambulation. This cycle is repeated as the amputee walks, thus creating a vacuum. Another downside with a vacuum suspension system is that any significant loss of vacuum may cause separation of the prosthetic socket from the residual limb.
It is advantageous to provide a mounting plate assembly providing superior comfort and stability to an amputee. It is beneficial to provide a mounting plate assembly offering improved reliability by limiting extraneous up and down motion, pivoting, rotation and shifting during use. Further, it is advantageous to provide extra durability to the prosthesis. The present disclosure addresses all of these aforementioned needs.